Remove hadolint rule code from location list entry text

The code is already passed with the code key of location list entry.
Before this change, when using the default message format, it appeared
twice in the description of each location list entry and twice in each
echo message.

Author: dmitrivereshchagin

ale_linters/dockerfile/hadolint.vim

@@ -49,7 +49,6 @@ function! ale_linters#dockerfile#hadolint#Handle(buffer, lines) abort
         if l:match[5] isnot# ''
             let l:code = l:match[4] . l:match[5]
             let l:link = ' ( ' . l:domain . l:code . ' )'
-            let l:text = l:code . ': ' . l:detail
             let l:detail = l:code . l:link . "\n\n" . l:detail
         else
             let l:type = 'E'

test/handler/test_hadolint.vader

@@ -17,23 +17,23 @@ Execute(The hadolint handler should handle a normal example):
   \     'col': 0,
   \     'type': 'W',
   \     'code': 'DL3006',
-  \     'text': "DL3006: Always tag the version of an image explicitly",
+  \     'text': 'Always tag the version of an image explicitly',
   \     'detail': "DL3006 ( https://github.com/hadolint/hadolint/wiki/DL3006 )\n\nAlways tag the version of an image explicitly",
   \   },
   \   {
   \     'lnum': 4,
   \     'col': 0,
   \     'type': 'W',
   \     'code': 'DL3033',
-  \     'text': "DL3033: Specify version with `yum install -y <package>-<version>`.",
+  \     'text': 'Specify version with `yum install -y <package>-<version>`.',
   \     'detail': "DL3033 ( https://github.com/hadolint/hadolint/wiki/DL3033 )\n\nSpecify version with `yum install -y <package>-<version>`.",
   \   },
   \   {
   \     'lnum': 12,
   \     'col': 0,
   \     'type': 'W',
   \     'code': 'SC2039',
-  \     'text': "SC2039: In POSIX sh, brace expansion is undefined.",
+  \     'text': 'In POSIX sh, brace expansion is undefined.',
   \     'detail': "SC2039 ( https://github.com/koalaman/shellcheck/wiki/SC2039 )\n\nIn POSIX sh, brace expansion is undefined.",
   \   },
   \ ],